A stereomicroscope, generally, comprises a microscope unit including objective lens groups and eyepiece lens groups, a base on which an observing stage is placed, and a focusing unit for moving said microscope unit up and down in a direction perpendicular to the base. The stereomicroscope, recently, has a trend to be folded smaller in height during unused time, because it is easy to carry outdoors or to keep in a narrower space. Although the eyepiece lens groups, when such a stereomicroscope is used, are considerably protruded from the microscope body, the eyepiece lens groups, when the stereomicroscope is carried or kept, are moved towards the base by turning the microscope unit upside down around a shaft supported by the focusing unit. When the stereomicroscope is carried or kept during unused time, a dust cover made of material such as rubber is fitted to an opening of the microscope unit, or the stereomicroscope is kept in a protecting case that houses the entire stereomicroscope, because otherwise dust or rain could enter the microscope unit through the opening.
There is a problem that the dust cover or protecting case could be lost outdoors or anywhere, because the dust cover or protecting case is a separate thing from the stereomicroscope. When the stereomicroscope is carried without the dust cover, with the microscope unit being turned upside down, it is inevitable that dust or rain enter the stereomicroscope through the opening and clings to the surface of an objective lens. Furthermore, there is another problem. Even if the dust cover or protecting case is not lost, users tend to carry the stereomicroscope without covering the opening, because it is troublesome to fit the dust cover to the opening or to put the stereomicroscope into the protecting case.
Thus, there are needs for a stereomicroscope that is able to prohibit dust or rain from entering the stereomicroscope and clinging to the lenses.